1. Field of the Invention
The present invention generally pertains to a cable reel structure incorporated into a steering system of a vehicle e.g. an automobile. The cable reel structure of the invention is defined by a fixed member and a mobile member, and a cable enclosure formed between the same. The cable enclosure of the present invention contains a cable guide having e.g. a ring-shape with at least one cut-out portion, which partitions the cable enclosure into an inner cable enclosure and an outer cable enclosure along the radial direction of the cable reel structure. The cable enclosure further includes a flat cable, which is spiraled in the inner cable enclosure in a first circular direction, U-turned around the cut-out portion of the cable guide, and then spiraled in the outer cable enclosure in a second circular direction reversed with respect to the first circular direction. Such a structural configuration allows the cable reel structure to be mounted more efficiently than in the case of the prior art.
2. Description of Background Information
In a conventional cable reel construction, the fixed member of the cable reel structure forms an outer cylindrical wall and top guard of the cable reel, and is immobilized with a combination switch body, which is in turn fixed with a steering column. On the other hand, the mobile member forms an inner cylindrical wall and bottom guard of the cable reel, and is fixed with the steering wheel. The mobile member is then mounted with the fixed member in a freely rotatable manner, thereby forming a substantially torus-shaped enclosure, in which a spiraled flat cable is stored. One end of the flat cable is connected to the fixed member, and the other end is connected to the mobile member, so that an electrical current flow in the flat cable can be led out from the cable reel to external circuits. The mobile member is rotated clockwise or counter-clockwise in conjunction with the movement of the steering wheel, and the spiraled flat cable is wound or unwound accordingly.
Such a cable reel is already disclosed in Japanese Patent Application published under No. Hei 7-193 955. As shown in FIGS. 1A and 1B, the prior art cable reel includes a torus-shaped enclosure 3 formed by a fixed member 1 and a mobile member 2. The torus-shaped enclosure 3 then contains a cable guide 4 with a reverse path channel 4a (forming a C shape), thereby defining radially inner and outer enclosures. A flat cable 5 is first spiraled in the inner enclosure formed between the inner cylindrical wall of mobile member 2 and the cable guide 4, U-turned after being passed through the reverse path channel 4a, and then spiraled in the reverse direction in the outer enclosure formed between the cable guide 4 and the outer cylindrical wall of fixed member 1
In the above reverse-type cable reel, when the steering wheel is rotated e.g. clockwise, the flat cable 5 is led from the outer enclosure into the inner enclosure by making a U-turn at the reverse path channel 4a of the cable guide 4, and wound around the inner cylindrical wall of the mobile member 2. When the steering wheel is rotated counter-clockwise, the flat cable 5 makes a reverse movement, i.e. the flat cable 5 is led into the outer enclosure of the cable reel, and added to the spirals in the outer enclosure from inside.
Compared with the system with normally spiraled flat cable, the reverse-type flat cable can have a shorter length. Normally, at least the length equivalent to the part of flat cable inversely turned at the exit of the reverse path channel can be shortened. The length of the flat cable can thus be reduced to at least half the length in the normally spiraled case.
In the above construction, the winding direction of the flat cable must be reversed between the outer enclosure and the inner enclosure when it is passed through the reverse path channel 4a of the cable guide 4. Meanwhile, the reverse path channel 4a is oriented in the radial direction of the cable guide 4 as shown in FIG. 1B. Accordingly, for the flat cable to be brought through the reverse path channel 4a, the cable guide 4 must be mounted into the cable reel from the top thereof (FIG. 1B).
However, as the slit width of the reverse path channel 4a is quite narrow, the flat cable tends to abut against edges 4b and 4c of the cable guide 4. As the flat cable 5 is made of a flexible material and is mechanically vulnerable, such an abutment often damages the flat cable.
Further, as the cable guide 4 must be fitted with the flat cable 5 in the top-down, or bottom-up, direction in a limited space, operations are not easy to conduct.
The present invention has been contemplated to solve such problems. It provides a reversed-type cable reel, for which the structure is configured such that a cable guide can be fitted with a flat cable without causing damage to the latter.
To this end, there is provided a reverse-type cable reel structure configured to contain at least one flat cable and including a cable guide with at least one reverse path channel, the cable guide partitioning the cable reel structure into a radially inner enclosure and a radially outer enclosure. The at least one flat cable is first wound in the radially inner enclosure in a given winding direction, passed through the reverse path channel, inversely turned at the exit thereof, and wound in the radially outer enclosure in a direction reverse to the given winding direction.
The cable guide is then divided into at least first and second complementary guide portions, thereby forming at least first and second reverse path channels, such that the complementary guide portions can be mounted laterally over the at least one flat cable after the latter has been wound in the radially inner enclosure.
Preferably, the cable reel structure includes a fixed member including an outer cylindrical wall, and a mobile member including an inner cylindrical wall, mounted within the fixed member in a freely rotatable manner, thereby defining a cable enclosure having a torus-shaped hollow portion. The cable enclosure contains the cable guide having a ring shape, the cable guide partitions the cable enclosure into the radially inner and external enclosures communicating therebetween through the reverse path channel, and the at least one flat cable has a first end portion fixed to the mobile member and a second end portion fixed to the fixed member, so that the first and second end portions of the at least one flat cable can be connected to external circuits.
Preferably yet, the reverse-type cable reel structure includes at least two flat cables, and the latter are passed through the respective at least first and second reverse path channels.
Typically, the at least two flat cables are fixed at different positions of the mobile member, so that the mobile member includes at least two loci connecting to the external circuits.
Alternatively, the first reverse path channel can be closed off. In this case, only one flat cable is used.
In the prior art, the cable guide is formed into the shape of C, and the slit portion in C-shape serves as the point where the flat cable is turned to a reverse direction. According to the present invention, the cable guide is divided into guide portions (subdivisions). The flat cable is first wound around the inner cylindrical wall of the mobile member. The guide portions are then laterally mounted onto the flat cable from the side of the cable reel, instead of from above as practiced in the past. The flat cable can thus be passed through the reverse path channels without difficulty. In other words, the flat cable is no longer inserted from above into the reverse path channel formed in the cable guide. Accordingly, the flat cable is not subjected to deformation or damage. Moreover, the flat cable and the cable guide can be assembled in a more restricted space than in the past.
In a preferred embodiment, two guide portions are prepared so as to form two reverse path channels. Two flat cables are then prepared and passed through the respective reverse path channels. In such a case, each of the two flat cables is first wound in the radially inner enclosure, and then wound inversely in the radially outer enclosure.
Alternatively, the guide portions can be mounted so as to form a single reverse path channel. The structure then resembles the C-shaped cable guide of the prior art, and only one flat cable is used.
When only one flat cable is used for containing many circuits, its width and height must be increased accordingly. Conversely, when two flat cables are used, an increased number of circuits can be handled with ease. For instance, the width of one flat cable can be kept narrow.
Besides, as already mentioned, the use of a reverse-type cable reel allows the length of each flat cable to be shortened. For this reason, a greater number of circuits can now be connected to a flat cable. The cable reel structure of the present invention is well adapted to such circumstances, and is suitable for miniaturizing the entire cable reel structure.
When the cable guide is divided into three guide portions, three reverse path channels may be formed and three flat cables may be used in a single cable reel structure. Consequently, the number of circuits can further be increased.